'98 Ranger 4.0L OHV Rebuild Boring Recommendations

[RhodesCD]

What would be the max boring recommendation for a '98 Ranger 4.0L OHV Rebuild.
Tony Morana says you can go 40 over but I've heard for a daily driver, you shouldn't go more the 30 over.
The plan is to move up to 10:1 with custom made forged pistons.

Just being safe...

 

[sgtsandman]

I can’t say yay or nay on the oversize boring but going 10:1 is probably going to force you into higher octane fuel. Technically the 4.0 SOHC at 9.5:1 should be but the timing is able to compensate enough for it. I don’t know if the OHV is able to do that or not.

 

[gaz]

@RhodesCD ,
First of all, anytime a rebore is done, the goal is to remove as little material as possible, thereby maintaining as much strength and product life, as possible, prolonging the engine's life.

If possible, I go for it 0.010" bore, second choice is 0.020" and if I have no other choice 0.030"; overbore is to reguvenate the system, not increase power or displacement. In a higher than stock compression ratio, the larger the bore, the more the compression is REDUCED, however slightly.